Electrolyte for long cycle life secondary battery and secondary battery containing the same

Abstract

Provided are a non-aqueous electrolyte for a secondary battery and a secondary battery including the same. The non-aqueous electrolyte for a secondary battery contains a non-aqueous solvent, a lithium salt, and a 2-thioxo-1,3-dithiole-4,5-dicarboxylate compound as an electrolyte additive, such that a secondary battery using the non-aqueous electrolyte for a secondary battery according to the present invention has an advantage in that room-temperature and high-temperature electrochemical characteristics and cycle life characteristics thereof are improved.

What is claimed is: 
     
         1 . A non-aqueous electrolyte for a lithium secondary battery comprising:
 a lithium salt;   a non-aqueous organic solvent; and   a 2-thioxo-1,3-dithiole-4,5-dicarboxylate compound represented by the following Chemical Formula 1:   
       
         
           
           
               
               
           
         
         (in Chemical Formula 1, R 1  and R 2  are each independently alkyl having 1 to 5 carbon atoms or alkenyl having 2 to 5 carbon atoms). 
       
     
     
         2 . The non-aqueous electrolyte for a lithium secondary battery of  claim 1 , wherein the 2-thioxo-1,3-dithiole-4,5-dicarboxylate compound of Chemical Formula 1 is contained at a content of 0.01 to 10 wt % based on a total weight of the electrolyte. 
     
     
         3 . The non-aqueous electrolyte for a lithium secondary battery of  claim 1 , wherein the 2-thioxo-1,3-dithiole-4,5-dicarboxylate compound of Chemical Formula 1 is selected from dimethyl 2-thioxo-1,3-dithiole-4,5-dicarboxylate, and divinyl 2-thioxo-1,3-dithiole-4,5-dicarboxylate. 
     
     
         4 . The non-aqueous electrolyte for a lithium secondary battery of  claim 1 , wherein the non-aqueous organic solvent is a linear carbonate-based solvent, a cyclic carbonate solvent, a linear ester solvent, a cyclic ester solvent, or a mixed solvent thereof. 
     
     
         5 . The non-aqueous electrolyte for a lithium secondary battery of  claim 4 , wherein the linear carbonate solvent is one or a mixture of two or more selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (EMC), and methylpropyl carbonate (MPC), the cyclic carbonate solvent is one or a mixture of two or more selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate (BC), 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate (VC), vinylethylene carbonate, and fluoroethylene carbonate, the linear ester solvent is one or a mixture of two or more selected from the group consisting of methyl propionate, ethyl propionate, propyl acetate, butyl acetate, and ethyl acetate, and the cyclic ester solvent is one or a mixture of two or more selected from the group consisting of gamma-butyrolactone, caprolactone, and valerolactone. 
     
     
         6 . The non-aqueous electrolyte for a lithium secondary battery of  claim 4 , wherein in the non-aqueous organic solvent, a mixed volume ratio of the linear carbonate solvent and the cyclic carbonate solvent is 1 to 9:1. 
     
     
         7 . The non-aqueous electrolyte for a lithium secondary battery of  claim 1 , wherein the lithium salt is one or a mixture of two or more selected from the group consisting of LiPF 6 , LiClO 4 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlO 4 , LiAlCl 4 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiN(C 2 F 5 SO 3 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , LiN(CF 3 SO 2 ) 2 , LiSCN, LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ) (x and y are 0 or natural numbers), LiCl, LiI, LiB(C 2 O 4 ) 2 , LiF 2 BC 2 O 4 , LiPF 4 (C 2 O 4 ), LiPF 2 (C 2 O 4 ) 2 , LiP(C 2 O 4 ) 3 , and LiPO 2 F 2 . 
     
     
         8 . The non-aqueous electrolyte for a lithium secondary battery of  claim 1 , wherein the lithium salt is contained at a concentration of 0.6 to 2.0 M. 
     
     
         9 . A lithium secondary battery comprising:
 a) a cathode containing a cathode active material capable of occluding and releasing lithium;   b) an anode containing an anode active material capable of occluding and releasing lithium;   c) the non-aqueous electrolyte for a lithium secondary battery of any one of  claims 1 ; and   d) a separator.